The specific aims of the proposed research are to develop and improve methodology for the use of existing data to assess surgical technology and innovation; to test this methodology in a pilot study of outcomes of total hip replacement; to develop information that may be of value in making health policy decisions involving total hip operations; and to study reoperations and other procedures associated with the primary operation and to analyze them in terms of patient characteristics, physician characteristics and hospital characteristics. To accomplish these aims we will use claims data on Medicare patients in Northern California. Data will be collected from four sources, the Medicare Payment Form, Operative Report, Beneficiary Medical Profile, and Generalized File Inquiry Form. Available data includes age and sex of patient, physician number and hospital number, preoperative and postoperative diagnosis, name of procedure, brand of prosthesis, side of body for which procedure was performed, medical complications for 90 days after initial surgery, orthopedic diagnoses and procedures for one year following initial surgery, and surgeon's fee. Results will be analyzed as a function of surgeon and hospital characteristics.